Reduction in sample injection bias using pressure gradients generated on chip.

Area of Science:

• Microfluidics
• Analytical Chemistry
• Electrophoresis

Background:

• Sample injection in microchip capillary zone electrophoresis (CZE) often suffers from bias due to electrophoretic mobilities and diffusion.
• Hydrodynamic flow injection requires precise pressure control, posing challenges in microfluidic systems.

Purpose of the Study:

• To develop a microchip device for electrokinetic pressure generation to minimize dead volume and injection bias.
• To enable precise control over sample zone introduction in CZE.

Main Methods:

• An electric field was applied across microchannels of differing depths to create electroosmotic flow mismatches.
• This generated pressure-driven flow was used for sample injection into the CZE channel.
• The injection strategy was integrated with CZE for amino acid analysis.

Main Results:

• The microchip device successfully generated pressure gradients on-chip.
• Narrow sample plugs with spatial standard deviations as low as 45 μm were achieved.
• Amino acid analysis using the integrated system yielded separation resolutions of 4-6.

Conclusions:

• Electrokinetic pressure generation offers a viable method to minimize injection bias in microchip CZE.
• The developed technique enables precise sample introduction, enhancing separation performance.
• This approach is effective for analyzing complex samples like amino acids.